Many vehicles, such as golf carts, include a governor system for limiting the degree of throttle to correspondingly limit the speed at which the vehicle may travel. Typically, vehicles include an engine, a transmission and a drive axle receiving drive torque from the engine, through the transmission. Generally, governor systems include a plurality of weights disposed about an input shaft of the drive axle, which are configured to pivot away from the input shaft as a result of the centrifugal forces generated by the angular velocity of the input shaft. The weights pivot outward against a set of sliding spacers, which in turn actuate a governor shaft extending inside the drive axle. As the angular velocity of the input shaft increases so does the centrifugal force, resulting in a torque produced through the governor shaft. Thus, the torque produced through the governor shaft is linear and directly proportional to the angular velocity of the input shaft.
A ground speed control mechanism, or governor system, is provided to limit the maximum vehicle speed. Traditional governor systems include a control arm with a pivotal box spring assembly, an accelerator cable input interconnecting the accelerator pedal and a throttle output interconnecting the throttle. The box spring assembly includes a threaded rod, a pivot bracket, a compression spring, spring retainers and an adjustment nut. The governed speed is preset by the manufacturer by adjusting the compression of the compression spring with the adjustment nut. A wire is then passed through a hole in the end of the threaded rod and a hole through the adjustment nut, the ends of which are soldered together as a means to maintain the governor setting over time.
When the accelerator pedal is actuated, the accelerator cable pulls on the box spring, which in turn applies a force to the control arm. The control arm then rotates and actuates the throttle linkage to open the throttle. As the accelerator is depressed and the vehicle accelerates, the torque exerted on the control arm by the governor shaft correspondingly increases. When this torque becomes greater than that produced by the box spring assembly, the control arm rotates, compressing the box spring further, thereby relieving the throttle linkage to enable closure of the throttle. As the vehicle slows, the torque exerted on the control arm by the governor shaft correspondingly decreases, enabling the control arm to rotate, thereby actuating the throttle linkage to again open the throttle. The result is a relatively constant vehicle speed, regardless of load.
The governor system described above, while functional, retains several disadvantages. The throttle linkage and its constituent components may be easily tampered with in order to increase the maximum speed of the vehicle. This generally results in the throttle not fully closing, causing engine back fire and poor low speed drivability. Other components wear over time leading to a significant loss in throttle travel preventing wide open throttle, thereby limiting hill climbing and other power intensive activities. Further, the overall complexity of the governor system results in tolerance stack-ups that require a long range of adjustment.
Therefore, it is desirable in the industry to provide an improved governor system for limiting a maximum vehicle speed. The improved governor system should be simple in construction, having a reduced number of components over traditional governor systems, for alleviating the disadvantages associated therewith. Further, the improved governor system should reduce the opportunity for tampering, to protect the engine and maintain drivability characteristics across all speed ranges.